Neato Botvac D SetConfig BatteryType 3 ??

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Neato Botvac D SetConfig BatteryType 3 ??

Postby szaplach » October 5th, 2018, 5:07 pm

I would like to convert my Botvac D80 to run on lithium batteries like I have for my two XV-14 robots. While the xv14 robots work great with my home made lithium batteries (with protection circuits), I can't figure out how to get the Botvac D to recognize it has lithium batteries in it.
The setconfig batterytype 3 command does not work in the botvac d, so my question is : are there any other commands that can be used? Or other ways to make this work other than buying an expensive lithium battery online?


Secondly, can anyone tell me the specs (voltage and exact current output) of the power brick inside the botvac D dock? My botvac did not come with a dock and I would like to covert one of my XV docks to a botvac dock if possible.

Thanks!
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Re: Neato Botvac D SetConfig BatteryType 3 ??

Postby glnc222 » October 5th, 2018, 10:44 pm

I suspect the Botvac firmware does not support configuring the battery type differently as in the XV models because the NImH version has a 12v system and the newer lithium models have a higher voltage similar to the XV -- needs checking. However, the higher per cell voltage of lithium cells does not divide well into 12v compared to the 15v systems. Anyway this is up to the firmware design, unknown so far.
There is a way to use lithium batteries in the Botvac without converting the software. LIthium was used, and is supplied commercially, for the XV models, using adapter circuitry which manipulates the NiMh charging control signals to satisfy lithium requirements -- the thermistor temperature reading which controls NIMh charging, vs voltage only controlling lithium charging.
It turns out as well that a superior type of lithium battery chemistry, LiFePo4 lasting several times the life of regular lithium ion batteries (just at the cost of having lower capacities per cell), has been successfully used in the Botvac, with some off the shelf circuit components. See thread http://www.robotreviews.com/chat/viewtopic.php?f=20&t=19149
This project used a newer model of LiFePo4 cells with higher capacity than I used in experiments with the XV model, where it would take more cells than would fit in the battery compartment to work properly. Details of interfacing lithium batteries to the NIMh charger are covered there, however. Thread http://www.robotreviews.com/chat/viewtopic.php?p=124772#p124772
The earliest adapters were used by a German hobbyist, at Roboter-Forum, consisting of a cell balancing module sold for other purposes, but whose balancing currents would heat up the board in a way the thermistor would get triggered when charging complete. The commercial lithium replacements use direct modification of the thermistor signal, synthesizing it. I showed simple circuits DIY to accomplish this. The components originally used in Germany became discontinued, and various other balancing products were used. See what the LiFePo4 project used.

Another advantage of LiFePo4 (lithium iron phosphate) is absence of the fire hazard requiring protection circuits for safety with regular lithium. LiFePO4 is used in electric bikes, solar power, and some robot lawn mowers with more room for the lower capacity cells.

Links above can be found in the Wiki index thread at top of the forum on Mods & Repairs.

The lower voltage of LiFePo4 cells allows useful division into the 12v in Botvac compared to the higher voltage regular lithium.

I think LIthiumPower Inc. supplying the first XV lithium replacements for NIMH has a Botvac version, but not clear how successful.
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Re: Neato Botvac D SetConfig BatteryType 3 ??

Postby glnc222 » October 6th, 2018, 10:56 am

The LIthiumPower Botvac replacement uses regular lithium ion cells, and with the problematic voltage fit to 12v, uses only an upper portion of the voltage discharge curve to match, with a lot of excess capacity to fit more into that range, inefficient. LiFePo4 gives a better fit. As the regular lithium wears, the first capacity lost will be that upper portion of the curve used.
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Re: Neato Botvac D SetConfig BatteryType 3 ??

Postby szaplach » October 6th, 2018, 6:30 pm

Thanks for the excellent info. I might have to look into the alternate lithium battery technology.
Also from the other links you provided I see the xv dock will not work with the botvac.
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Re: Neato Botvac D SetConfig BatteryType 3 ??

Postby glnc222 » October 6th, 2018, 9:31 pm

The 12v NiMH Botvac has an 18v charger and the 15v XV system has 24v chargers. The charger supplies a variable voltage step down buck voltage converter inside the bot, a sort of switching power supply similar to the power brick itself, which adjusts voltage on the battery to maintain a constant 2 amp charging current as the battery fills, gradually increasing voltage. The charging voltage can be 1-2v higher than the charged battery voltage, to push in charge. The XV battery terminal voltage was observed peaking around 18.5v when charging, falling to 16.5 as the charger is withdrawn. The 12v Botvac system may go only up to 14v or less. Lithium charging terminates at a maximum specified voltage for cells (over voltage would damage); NiMh charging terminates when temperature rises faster than 1C per minute, though is followed by a lower current topping off cycle -- very convoluted compared to lithium.

The lithium charging algorithm can be tested with the NiMh cells, as the lithium charging terminates at a much lower voltage and you will see the under charged NiMh cells. Important to see the system would not over charge, over voltage lithium cells. Protection boards with guards for over and under voltage (excess discharge) are standard with lithium packs, and monitor continuously for initial testing. With LiFePo4 cells could be damaged but nothing else; with regular lithium, cells can catch fire or explode (on aircraft sealed in fireproof vaults). Apparently if they get hot a runaway positive feedback internal discharge can occur, also from any contamination of the materials. The danger has required restrictions on air freight of lithium batteries; surface shipping required, after famous disasters.

(Also why you need spotwelded tabs on lithium cells bought, no soldering to heat them up, care required assembling packs; LiFePo4 more flexible, same as NiMh).

The newer lithium type used in power tool packs are safer, and still have the higher energy density than LifePo4. DIY XV replacements with SetConfig have used those, better grade lithium cells more expensive. I forget the name off hand, see threads on those projects. They are always cooking up new witches brew battery chemistries.

NiMh Botvac pack prices have fallen pretty low. Not clear whether lithium replacements worthwhile. A matter of taste. LiFePo4 though, could theoretically last the lifetime of the vacuum, several years.
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